Chemical-mechanical polishing (“CMP”) processes are used in the manufacturing of microelectronic devices to form flat surfaces on semiconductor wafers, field emission displays, and many other microelectronic substrates. For example, the manufacture of semiconductor devices generally involves the formation of various process layers, selective removal or patterning of portions of those layers, and deposition of yet additional process layers above the surface of a semiconducting substrate to form a semiconductor wafer. The process layers can include, by way of example, insulation layers, gate oxide layers, conductive layers, layers of metal or glass, and the like. In certain steps of the wafer fabrication process, the uppermost surface of the process layers is desirably planar, i.e., flat, for the deposition of subsequent layers. CMP is used to planarize process layers wherein a deposited material, such as a conductive or insulating material, is polished to planarize the wafer for subsequent process steps.
In a typical CMP process, a wafer is mounted upside down on a carrier in a CMP tool. A force pushes the carrier and the wafer downward toward a polishing pad. The carrier and the wafer typically are rotated above the rotating polishing pad on the CMP tool's polishing table. A polishing composition (also referred to as a polishing slurry) generally is introduced between the rotating wafer and the rotating polishing pad during the polishing process. The polishing composition typically contains one or more chemicals that interact with or dissolve portions of the uppermost wafer layer(s) and one or more abrasive materials that physically remove portions of the layer(s). The wafer and the polishing pad can be rotated in the same direction, in opposite directions, or one of the wafer or polishing pad can be rotated while the other one of the wafer or polishing pad remains stationary. The carrier also can oscillate across the polishing pad on the polishing table. The rotation scheme is chosen according to the particular polishing process being carried out.
The polishing pad typically is made of a rigid, micro-porous material, and the polishing pad typically performs several useful functions during a polishing process, such as polishing slurry transport, distribution of applied pressure across a substrate to be polished, and removal of material abraded from substrate. The physical and mechanical properties of the polishing pad, such as the polishing pad material, the surface topography of the polishing pad (e.g., micro- and macro-structures, such as perforations, pores, textures, grooves, depressions, etc.), and the like, in combination with the properties of the composition of the polishing slurry (e.g., reactivity, abrasiveness, etc.), can affect various aspects of the CMP process, including the polishing rate and the quality of the polished substrate (e.g., degree of planarity, and number and type of defects). The polishing rate, in particular, directly relates to the throughput of the CMP process, such that the polishing rate is important for cost-of-ownership considerations.
Attempts in the art to increase throughput by way of increasing the polishing rate have typically involved adjusting the physical and mechanical properties of the polishing pad material or the micro-structure of the polishing pad surface, e.g., using different materials and pad conditioning processes, often resulting in various undesirable tradeoffs, such as increased defects on the surface of the polished substrate and/or reduced life of the polishing pad. While employing macro-structures on the polishing pad surface, such as grooving patterns, has had some success in improving some characteristics of the polishing process, such as the lifetime of the polishing pad in some instances (see, for example, U.S. Pat. No. 6,520,847 to Osterheld et al.), other properties of the polishing process, such as the polishing rate of the substrate, generally have not been adequately improved by conventional grooving patterns to sufficiently increase throughput, while still achieving a polished substrate with a high level of planarity and low defects. Moreover, many conventional grooving patterns are not adequate for retaining the polishing slurry on the polishing pad for a sufficient amount of time thereby requiring a larger amount of polishing slurry to be used in a polishing process, which undesirably adds to the overall manufacturing costs.
Thus, there remains a need in the art for improved polishing pads that retain the polishing slurry for a sufficient amount of time and also achieve a commercially viable polishing rate, while at the same time producing a polished substrate having, advantageous surface properties, such as high planarity and low defects.